To reduce the particle emissions of a diesel engine, use is made of soot particle filters. For example, to monitor the effectiveness of said filters, sensors are used which measure the particle content of the exhaust gases flowing through the filter.
At present, resistance particle sensors are known in which two or more metallic electrodes are formed, wherein the particles, in particular soot particles, that are accumulated cause the electrodes, which engage into one another in a comb-like manner, to be short-circuited, and therefore, with increasing particle concentration on the sensor surface, a decreasing resistance or a decreasing impedance (or an increasing current if a constant voltage is applied) can be measured between the electrodes. The measured current or the change thereof can be correlated with the accumulated mass of particles and therefore also with the particle concentration prevailing in the exhaust gas.
Sensors or systems of said type are known for example from DE102008041809A1 and EP1873511A2/A3.
In general, the particle or solid body sensor may be used in the exhaust system to detect solid and also soluble fractions in the exhaust-gas flow. For this purpose, use is conventionally made of a resistance element whose resistance varies when substances from the exhaust gas precipitate on the sensor element. This requires regular regeneration of the sensor by periodically increasing the temperature of the sensor element in order to evaporate the accumulated material. The derivative of the sensor signal with respect to time may be used to calculate the mass throughflow of the solid or soluble materials in the exhaust gas. However, the size of the particles within the exhaust flow cannot be determined with this conventional type of sensor.
The inventors herein have recognized the issues with the above approach and offer a particle sensor to at least partly address them. In one embodiment, a particle sensor for an exhaust system comprises at least two inlet openings for an exhaust-gas flow of the exhaust system, wherein the at least two inlet openings are of different sizes, and at least two sensor elements, wherein in each case one sensor element is arranged downstream of one inlet opening.
In this way, the relative portion of different sized particles within the exhaust may be determined. In some examples, the distribution of particle sizes within the exhaust may be monitored, and a change in the distribution that exceeds a threshold may indicate a degraded combustion condition, which may be mitigated by adjusting one or more engine operating parameters.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.